Problem: 6 rubber stamps cost $8.16. Which equation would help determine the cost of 11 rubber stamps?
Solution: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 6 rubber stamps. We want to know the cost of 11 rubber stamps. We can write the numbers of rubber stamps as a proportion: $\dfrac{6}{11}$ We know 6 rubber stamps costs $8.16. We can let $x$ represent the unknown cost of 11 rubber stamps. The proportion of these costs can be expressed as: $\dfrac{\$8.16}{x}$ The cost changes along with the number of rubber stamps purchased, and so the two proportions are equivalent. $\dfrac{6}{11} = \dfrac{\$8.16}{x}$